Laser beam machining device

ABSTRACT

A laser material processing apparatus for processing a workpiece ( 22 ) in such a way as to separate one laser light ( 26 ) into two laser beams ( 26   a,    26   b ) via first polarizing means ( 25 ), one laser beam being passed via the mirrors ( 24 ), the other laser beam being scanned biaxially by a first galvano scanner ( 29 ), and conduct two laser beams ( 26   a,    26   b ) to second polarizing means ( 27 ) for scanning via a second galvano scanner ( 30 ), wherein an optical path is constituted such that the laser beam ( 26   b ) transmitted through the first polarizing means ( 25 ) is reflected by the second polarizing means ( 27 ), and the laser beam ( 26   a ) reflected by the first polarizing means ( 25 ) is transmitted through the second polarizing means ( 27 ).

TECHNICAL FIELD

[0001] The present invention relates to a laser material processingapparatus mainly intended for drilling the workpiece such as a printedboard to improve the productivity.

BACKGROUND ART

[0002]FIG. 8 is a schematic constitutional view showing the conventionallaser material processing apparatus for drilling.

[0003] In FIG. 8, reference numeral 1 denotes a workpiece such as aprinted board, 2 denotes a laser beam for drilling the workpiece 1 tomake a via hole or through hole, 3 denotes a laser oscillator foroscillating the laser beam 2, 4 denotes a plurality of mirrors forreflecting the laser beam 2 along the optical path, 5 and 6 denote agalvano scanner for scanning the laser beam 2, 7 denotes an fθ lens forfocusing the laser beam 2 on the workpiece 1, and 8 denotes an XY stagefor moving the workpiece 1.

[0004] In the typical laser material processing apparatus for drilling,the laser beam 2 oscillated from the laser oscillator 3 is conducted viaa necessary mask and the mirrors 4 to the galvano scanners 5, 6 andfocused via the fθ lens 7 at a predetermined position of the workpiece 1by controlling the deflection angle of the galvano scanners 5, 6.

[0005] The deflection angle of the galvano scanners 5, 6 via the fθ lens7 is limited to a range of 50 mm square, for example. Therefore, thelaser beam 2 is focused at the predetermined position of the workpiece 1by controlling the XY stage 8 as well, thereby allowing the workpiece 1to be machined in a broader range.

[0006] Herein, the productivity of the laser material processingapparatus is closely related with the drive speed of the galvanoscanners 5, 6 and the processing area of the fθ lens 7.

[0007] To improve the drive speed of the galvano scanner, it iseffective to change the design of an optical system by reducing the massof a galvano mirror fixed to the rotation shaft of the galvano scannerand driven by controlling the deflection angle, or varying the distancebetween the galvano scanners 5, 6 and the fθ lens 7, and to reduce thedeflection angle while the processing range is maintained. However, ifthe mirror diameter of the galvano scanner is made smaller to reduce themass of the galvano mirror, the laser beam 2 has its peripheral portionintercepted by a mask in passing through the mask, and the diameter oncereduced, but the laser beam 2 is broadened in diameter due todiffraction after passing through the mask, and has a larger diameterthan the galvano mirror when arriving at the galvano mirror of thegalvano scanner 5, 6, causing a part of the laser beam 2 to get out ofthe galvano mirror, so that an image of the mask is not correctlytransferred onto the workpiece 1, whereby the micro hole fabrication isnot made.

[0008] Also, the deflection angle of the galvano scanners is reducedwhile the processing range is maintained in such a way as to change theoptical design, including changing the positional relation between thefθ lens and the galvano scanners. However, it takes a lot of time todesign, and it is required to change the specification of the veryexpensive fθ lens or the design of the overall optical system, wherebyit was difficult to improve the productivity easily and cheaply with asingle beam.

[0009] A laser material processing apparatus of the previously describedtype intended to improve the productivity was disclosed inJP-A-11-314188, for example.

[0010]FIG. 9 is a schematic constitutional view of the laser materialprocessing apparatus as disclosed in JP-A-11-314188.

[0011] In FIG. 9, reference numeral 9 denotes a workpiece, 10 denotes amask, 11 denotes a half-mirror for separating a laser light, 12 denotesa dichroic mirror, 13 a denotes a laser beam reflected from thehalf-mirror, 13 b denotes a laser beam transmitted through thehalf-mirror and reflected from the dichroic mirror, 14 and 15 denote themirrors, 16 denotes an fθ lens for focusing the laser beams 13 a and 13b onto the workpiece 9, 17 and 18 denote galvano scanners for conductingthe laser beam 13 a to a processing area A1, 19 and 20 denote galvanoscanners for conducting the laser beam 13 b to a processing area A2, and21 denotes an XY stage for moving each part of the workpiece to theprocessing area A1 or A2.

[0012] The laser material processing apparatus as shown in FIG. 9separates the laser light passing through the mask 10 via thehalf-mirror 11 into plural beams, conducts the separated laser beams 13a and 13 b to a plurality of galvano scanner systems arranged on theincident side of the fθ lens 16, and scans the laser beams 13 a and 13 bwith the plurality of galvano scanner systems to be applied to thedivided processing areas A1 and A2.

[0013] The separated laser beam 13 a is introduced via the first galvanoscanner system 17, 18 into a half area of the fθ lens 16. Also, theother separated laser beam 13 b is introduced via the second galvanoscanner system 19, 20 into a remaining half area of the fθ lens 16. Thefirst and second galvano scanner systems are arranged in symmetry aboutthe central axis of the fθ lens 16, whereby the half parts of the fθlens 16 are employed at the same time to improve the productivity.

[0014] However, in the apparatus as disclosed in JP-A-11-314188, thefirst galvano scanner system 17, 18 and the second galvano scannersystem 19, 20 scan the laser beams, into which laser light is separatedvia the half mirror 11, to be applied on the processing areas A1 and A2that are divided. Therefore, a dispersion in the quality of processedholes is likely to occur due to a difference between reflection from andtransmission through the half mirror 11 between the laser beams 13 a and13 b, into which laser light is separated by the half mirror 11.

[0015] For example, when there is an energy difference between theseparated laser beams 13 a and 13 b, a difference in the hole diameteror hole depth of the processed holes is likely to occur on the workpiece9. Therefore, there is the possibility that the strict requirements forprocessing the hole are not satisfied in terms of the dispersion in thehole diameter.

[0016] Herein, when the laser beam 13 a has a higher energy than thelaser beam 13 b, it is required to adjust the energy of laser beam 13 bto be decreased by further adding an expensive optical component such asan optical attenuator on the optical path of laser beam 13 b. Theoptical component such as the optical attenuator must be produced in thespecification of removing the energy at a certain percentage. Forexample, when the specification of removing the energy of 5% and thespecification of removing the energy of 3% are required, two kinds ofoptical attenuator are produced. Thereby, the optical attenuator isprepared in a few kinds of specification, and exchanged every time theenergy difference is adjusted.

[0017] Also, in the optical path constitution as shown in FIG. 9, therewas a problem that the optical path lengths of laser beams 13 a and 13b, into which laser light is separated after passing through the mask10, up to the workpiece 9 are different, so that the strict beam spotdiameters on the workpiece 9 are different.

[0018] Moreover, the fθ lens 16 is equally divided, and the dividedprocessing areas A1, A2 are machined at the same time. Therefore, whenthe number of processed holes in the processing areas A1 and A2 isgreatly varied, or when there is no processed hole of object in eitherthe processing area A1 or A2 such as an end portion of the workpiece, itis not expected to improve the productivity.

DISCLOSURE OF THE INVENTION

[0019] This invention has been achieved to solve the above-mentionedproblems, and it is an object of the invention to provide a lasermaterial processing apparatus in which a difference in the energy orquality between separated laser beams is minimized to provide an equaloptical path length and an equal beam spot diameter for the separatedlaser beams, and the separated laser beams are applied on the same areato improve the productivity less expensively.

[0020] In order to achieve the above object, according to a first aspectof the invention, there is provided a laser material processingapparatus for processing a workpiece in such a way as to separate onelaser light into two laser beams via first polarizing means, one laserbeam being passed via the mirrors, the other laser beam being scannedbiaxially by a first galvano scanner, and conduct two laser beams tosecond polarizing means for scanning via a second galvano scanner,characterized in that an optical path is constituted such that the laserbeam transmitted through the first polarizing means is reflected by thesecond polarizing means, and the laser beam reflected by the firstpolarizing means is transmitted through the second polarizing means.

[0021] Also, two polarizing means are arranged so that the reflectionsurfaces may be opposed to each other to form an optical path in whichthe separated laser beams have the equal optical path length.

[0022] Also, a stationary portion of polarizing means is provided with arotating mechanism around an axis perpendicular to a surface containingthe axes of two separated laser beams.

[0023] Also, an energy balance of the laser beam is adjusted by changinga transmission factor of the laser beam transmitted through polarizingmeans by rotation of the rotating mechanism.

[0024] The laser beam selecting means is provided for selecting anylaser beam from among the separated laser beams.

[0025] Also, the laser beam selecting means controls a shutter providedon the optical path of each of the separated laser beams to be opened orclosed to take out the laser beam from any optical path.

[0026] Also, detection means is provided for detecting an energy balanceof laser beam on each optical path, in which the energy balance of eachlaser beam detected by the detection means is adjusted to be almostequivalent.

[0027] Also, the detection means consists of a power sensor providednear an XY table on which the workpiece is laid.

[0028] Also, the separated laser beams have the equal optical pathlength between the first polarizing means and the second polarizingmeans.

[0029] Also, the deflection angle by which the first galvano scannerscans is smaller than the deflection angle by which the second galvanoscanner scans.

[0030] Also, each laser beam is reflected by the same number of mirrorson each optical path formed between the first polarizing means and thesecond polarizing means.

[0031] Also, third polarizing means is provided between a laseroscillator and the first polarizing means, in which two laser beamsseparated by the third polarizing means are conducted to the firstpolarizing means and the second polarizing means and further separatedinto 2n components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a view schematically showing an optical pathconstitution of a laser material processing apparatus according to anembodiment of the present invention.

[0033]FIG. 2 is an enlarged view and a structural view of a portion forreflecting and transmitting the laser beam in a polarized beam splitterwithin the optical path constitution of the laser material processingapparatus according to the embodiment of the invention.

[0034]FIG. 3 is a graph showing the dependency of reflection andtransmission factors on an incident angle of laser beam in the polarizedbeam splitter according to the embodiment of the invention.

[0035]FIG. 4 is a flowchart of a program for automatically correctingthe deflection angle of a galvano scanner.

[0036]FIG. 5 is a flowchart of a program for automatically adjusting theangle of the polarized beam splitter.

[0037]FIG. 6 is a view showing the schematic constitution of an exampleof the laser material processing apparatus when four laser beams areemployed to perform the processing by adding polarizing means.

[0038]FIG. 7 is a flowchart of a program for automatically correctingthe deflection angle of the galvano scanner.

[0039]FIG. 8 is a view showing the schematic constitution of theconventional laser material processing apparatus for drilling.

[0040]FIG. 9 is a view showing the schematic constitution of theconventional laser material processing apparatus for drilling intendedto improve the productivity.

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

[0041]FIG. 1 is a schematic constitutional view showing a laser materialprocessing apparatus according to an embodiment of the presentinvention.

[0042] In FIG. 1, reference numeral 22 denotes a workpiece such as aprinted board, 23 denotes a mask for forming an image to transfer adesired processing shape (e.g., circle) onto the workpiece 22, 24denotes a plurality of mirrors for reflecting a laser beam along theoptical path, 25 denotes a first polarized beam splitter as firstpolarizing means for separating a laser light, 26 a denotes a laser beamreflected from the first polarized beam splitter, 26 b denotes a laserbeam transmitted through the first polarized beam splitter, 27 denotes asecond polarized beam splitter as second polarizing means fortransmitting the laser beam 26 a and reflecting the laser beam 26 b, 28denotes an fθ lens for focusing the laser beams 26 a and 26 b onto theworkpiece 22, 29 denotes a first galvano scanner for scanning the laserbeam 26 a biaxially to be conducted to the second beam splitter, 30denotes a second galvano scanner for scanning the laser beams 26 a and26 b biaxially to be conducted to the workpiece 22, 31 denotes an XYstage for moving the workpiece 22, 34 denotes a shutter as laser beamselecting means provided on the optical path of laser beam andintercepting the laser beam, 35 denotes a power sensor for measuring theenergy of laser beam emergent from the fθ lens 28, 36 denotes a CCDcamera that is an image pickup device for measuring the hole diameter orposition of a processed hole by the laser beam, and 37 denotes aworkpiece for correcting the deflection angle of galvano scanner.

[0043]FIG. 2 shows a portion for reflecting or transmitting the laserbeam in the polarized beam splitter 25 or 27. Reference numeral 32denotes a window for reflecting or transmitting the incident light, 33denotes a mirror for causing an incident light component reflected fromthe window 32 to be reflected at an angle of 90° relative to theincident light, 41 denotes a servo motor having a rotation axis disposedat a position where the emergent angle and position of laser beam areunchanged even if the incident angle of laser beam on the polarized beamsplitter is changed, 42 denotes a bracket for securing the servo motor41, and 43 denotes a bracket for connecting the polarized beam splitterand the servo motor.

[0044] For the window portion 32 of the polarized beam splitter 25, 27,a material ZnSe is often employed in a case of CO₂ laser, but othermaterials such as Ge may be employed.

[0045] In this invention, the oscillated laser light is circularlypolarized and conducted to the first polarized beam splitter 25 forseparation into the laser beam 26 b that is P wave transmitted throughthe first polarized beam splitter in a polarization direction parallelto the incident plane and the laser beam 26 a that is S wave reflectedin a polarization direction perpendicular to the incident plane.

[0046] The laser beam conducted to the first polarized beam splitter 25may be linearly polarized, but not circularly polarized, to make anangle of 45° relative to the polarization directions of P wave and Swave.

[0047] Herein, when either the circularly polarized light or thelinearly polarized light is conducted to the first polarized beamsplitter, it is required to oscillate the laser light of linearpolarization from the laser oscillator.

[0048] In order to conduct the laser light of circular polarization tothe first polarized beam splitter 25, it is required to employ aretarder for changing the linearly polarized light to the circularlypolarized light on the optical path, whereby the laser light is incidentat an angle of 90° between the incident light and the reflected light inthe retarder. Also, the polarization direction of laser light incidenton the retarder must make an angle of 45° relative to the line ofintersection between a plane made by the optical axis of incidence andthe optical axis of reflection as two sides and a reflection surface ofthe retarder. However, the laser light of circular polarization includesevenly the polarization directions of P wave and S wave, and there is nolimitation on the polarization direction when conducting the laser beamto the first polarized beam splitter 25, whereby the optical path isdesigned with a high degree of freedom.

[0049] On the other hand, when the linearly polarized light is employed,it is required to conduct the laser light to the first polarized lightbeam splitter 25 as the linearly polarized light making an angle of 45°relative to the polarization directions of P wave and S wave separatedby the first polarized beam splitter, as previously described. Thoughthere is a limitation on the design of the optical path, it isunnecessary to provide the retarder and an adjusting mechanism foradjusting the polarization direction of laser beam incident on theretarder, and the angle of optical axis, and to make the adjustments,whereby it is possible to simplify the optical path to contribute toreduction of the cost.

[0050] The laser beam 26 b transmitted through the first polarized beamsplitter 25 is conducted via the bend mirrors 24 to the second polarizedbeam splitter 27. On the other hand, the laser beam 26 a reflected fromthe first beam splitter 25 is caused to scan biaxially by the firstgalvano scanner 29, and conducted to the second polarized beam splitter27.

[0051] Thereafter, the laser beams 26 a, 26 b are caused to scanbiaxially by the second galvano scanner 30, and applied on the workpiecethrough the fθ lens 28.

[0052] At this time, the laser beam 26 a is applied at the same positionon the workpiece as the laser beam 26 b by scanning of the first galvanoscanner 29.

[0053] Also, the laser beams can be applied at different two points onthe workpiece via the second galvano scanner 30 by causing the laserbeam 26 a to scan within a preset range for the laser beam 26 b, forexample, within a range of 4 mm square around the laser beam 26 b byscanning of the galvano scanner 29 in view of the characteristics of thewindow 32 for the beam splitter.

[0054] The laser beam 26 a reflected from the first polarized beamsplitter 25 is transmitted through the second polarized beam splitter27, and the laser beam 26 b transmitted through the first polarized beamsplitter is reflected from the second polarized beam splitter 27.

[0055] Therefore, two separated laser beams are passed through both thereflection and transmission processes, whereby it is possible to offseta variation in the quality of laser beam or a breakdown in the energybalance.

[0056] For example, the reflection and transmission factors in thepolarized beam splitter are given near the Brewster angle in which theincident angle of laser beam on the polarized beam splitter is ideal, asshown in FIG. 3.

[0057] The longitudinal axis of FIG. 3 is the reflection factor and thetransmission factor, which indicate 100% when the incident laser lightis fully divided into two beams. For example, when the reflection factoris 100%, the percentage of reflected light to the incident light is 50%.

[0058] When the incident angle of laser beam has an error of −2° withrespect to the Brewster angle for two polarized beam splitters, thereflection factor of laser beam is 99% and the transmission factor is97% for each polarized beam splitter. The energies of two laser beamsobtained through the reflection or transmission process twice are 98%and 94%, producing an energy difference of 4%, while the energies oflaser beams obtained through both the reflection and transmissionprocesses once are both 96%. By making the optical path as previouslydescribed, it is possible to offset the characteristics.

[0059] Also, two polarized beam splitters may be identical, whereby theoffset effect is facilitated to contribute to reduction of the cost.

[0060] Two polarized beam splitters are arranged, as shown in FIG. 1, sothat the optical path lengths of the laser beams 26 a and 26 b betweenthe first polarized beam splitter 25 and the second polarized beamsplitter 27 are equal. Thereby, the beam spot diameters of two separatedlaser beams are equalized.

[0061] For example, in this embodiment of the invention, when theoptical path is decomposed into X, Y and Z directions, the same opticalpath length is obtained. Therefore, when the design of optical pathcomponents is changed dimensionally, the optical path can be extended orcontracted in the X, Y and Z directions, whereby the optical pathlengths of laser beams 26 a and 26 b are kept invariant.

[0062] Also, the polarized beam splitter is integrated with the mirror33, so that the reflected light may be emergent at 90° with respect tothe incident angle, as shown in FIG. 2.

[0063] A stationary portion of the polarized beam splitter has astructure in which a rotating mechanism is provided around the axisperpendicular to the plane containing the axes of two separated laserbeams 26 a and 26 b, as shown in FIG. 2. When there is an energydifference between two separated laser beams 26 a and 26 b, the energydifference is adjusted using the dependency of reflection factor andtransmission factor on the incident angle of laser beam, as shown inFIG. 3. The precision of energy balance of two laser beams 26 a and 26 bafter passing through two polarized beam splitters is enhanced in aninexpensive way without needing the other optical components such as anoptical attenuator.

[0064] Also, the rotation axis is located at the position where theemergent position is unchanged even if the incident angle on thepolarized beam splitter is changed. Even if the polarized beam splitteris rotated to adjust the energy balance, it is managed to minimize achange in the angle or position of succeeding optical path.

[0065] For example, in the case where the rotation axis is arranged at apoint of intersection between the window 32 and the mirror 33 in FIG. 2,when the polarized beam splitter is rotated by ±5°, the incident angleof laser beam on the window 32 is increased, but the incident angle onthe mirror 33 is decreased. Or the incident angle of laser beam on thewindow 32 is decreased, but the incident angle on the mirror 33 isincreased. The emergent angle of the laser beam being incident on thepolarized beam splitter is 90° without error by offsetting an angleerror, and there is no variation in the emergent position. Thereby, thiseffect is similarly provided, whether the window 32 or the mirror 33 forthe polarized beam splitter is on the incident side.

[0066] Owing to the relationship between the reflection and transmissionfactors and the incident angle in the polarized beam splitter as shownin FIG. 3 and the above effect, when the energy of laser beam 26 areflected from the first polarized beam splitter 25 is high, the energyis decreased by rotating the second polarized beam splitter 27, andadjusting the transmission factor of laser beam 26 a. Also, when theenergy of laser beam 26 b transmitted through the first polarized beamsplitter 25 is high, the energy is decreased by rotating the firstpolarized beam splitter 25, and adjusting the transmission factor oflaser beam 26 b. Thereby, the later adjustment for the optical path isunnecessary, and the maintenance time is shortened.

[0067] Referring to FIG. 4, a flow for automatically adjusting the angleof the polarized beam splitter to control the energy balance of laserbeams will be described below.

[0068] First of all, the power sensor 35 is moved to the position wherea light receiving portion of the power sensor 35 fixed on the XY stage31 can receive laser beam emergent from the fθ lens 28 (step S1).

[0069] Thereafter, the first shutter 34 a is opened, and the secondshutter 34 b is closed (step S2). Then, a laser light is emitted fromthe laser oscillator, not shown, and an energy of the laser beam 26 a ismeasured by the power sensor 35 (step S3).

[0070] After measuring the energy, the oscillation of laser light isonce stopped, the first shutter 34 a is closed, and the second shutter34 b is opened (step S4).

[0071] By emitting laser light again, an energy of laser beam 26 b ismeasured by the power sensor 35 (step S5).

[0072] An energy difference between two laser beams 26 a and 26 bmeasured by a control device is calculated (step S6). If it is within atolerance value, the adjustment is ended. However, if it is out of thetolerance value, the first polarized beam splitter 25 and the secondpolarized beam splitter 27 are rotated to adjust the transmission factorof each polarized beam splitter (step S9), whereby the adjustment isrepeated by measuring the energies of two laser beams again until it iswithin the tolerance value.

[0073] Also, it is determined whether or not the tolerance value ofenergy difference is within a preset range of rotation angle for thepolarized beam splitter, for example, within a range of ±5° (step S8).If it is not within the preset range, the circular polarization factoris reduced when the laser light of circular polarization is conductedfrom the laser oscillator, or when the laser light of linearpolarization is conducted, it is judged that the apparatus is in acondition requiring the maintenance for the angle deviation in thepolarization direction in which laser beam is conducted at an angle of45° with respect to the polarization direction of transmission orreflection in the first polarized beam splitter 25, whereby the programis ended, and a message indicating that the program is abnormally endedand prompting the maintenance is displayed on the operation screen, notshown.

[0074] This automatic adjustment for the angle of the polarized beamsplitter is made periodically, for example, at the time of setup orstarting the apparatus. Thereby, the energy balance of laser beams isalways maintained at high precision, and the worker does not need theskills, thereby performing the stable machining.

[0075] Referring to FIG. 5, a flow for making the automatic correctionfor the deflection angle of the galvano scanner to maintain or improvethe precision of processing position is shown.

[0076] First of all, the workpiece 37 (e.g., acrylic plate) forcorrection that is placed beforehand on the XY stage 31 is moved to theprocessing area of the fθ lens 28. The second shutter 34 b is opened,and the first shutter 34 a is closed (step S11). The laser beam 26 b iscaused to scan by the second galvano scanner 30, the machining beforecorrecting the deflection angle of the second galvano scanner 30 is madewithin a preset range, for example, within a range of 50 mm square ofthe workpiece (step S12).

[0077] After making the machining, the positional precision of processedhole is measured with the CCD camera 36 by driving the XY stage 31 (stepS13).

[0078] By comparing the measurement result with the reference position,the correction value for the deflection angle of the second galvanoscanner 30 is calculated in the control device, not shown (step S14).

[0079] Thereafter, the XY stage 31 is driven to move the workpiece 37for correction within the processing area of the fθ lens 28, whereby theworkpiece 37 is machined after correcting the deflection angle of thesecond galvano scanner 30 (step S15).

[0080] After making the machining, the positional precision of processedhole is measured with the CCD camera 36 by driving the XY stage 31 (stepS16), and compared with the preset tolerance value (step S17). When itis out of the tolerance value, the program is ended to inform theoperator that the apparatus has the abnormality or there is an error inusage of the method, and a message with the contents indicating that theprogram is abnormally ended is displayed on the operation screen, notshown.

[0081] On the other hand, within the tolerance value, the correction forthe deflection angle of the second galvano scanner 30 is ended, and thecorrection for the deflection angle of the first galvano scanner 29 ismade.

[0082] In correcting the deflection angle of the first galvano scanner29, the first shutter 34 a is opened, and the second shutter 34 b isclosed (step S18). Thereby, the laser beam 26 a alone is caused to scanby the first galvano scanner 29 and the second galvano scanner 30, inwhich the machining before correcting the deflection angle of the firstgalvano scanner 29 is made in the same range as at the time ofcorrecting the deflection angle of the second galvano scanner 30 (stepS19).

[0083] For example, the first galvano scanner 29 controls the laser beam26 a to scan in a range of 4 mm square around the laser beam 26 b, andthe second galvano scanner 30 controls the laser beam 26 a to scan in arange of 46 mm square around the laser beam 26 a, whereby the laser beam26 a passed via the first and second galvano scanners 29 and 30 makesthe machining in a range of 50 mm square.

[0084] After making the machining, the positional precision of processedhole is measured with the CCD camera 36 by driving the XY stage 31 (stepS20)

[0085] By comparing the measurement result with the reference position,the correction value for the deflection angle of the first galvanoscanner 29 is calculated in the control device (step S21).

[0086] Thereafter, the XY stage 31 is driven to move the workpiece 37for correction within the processing area of the fθ lens 28, whereby theworkpiece 37 is machined after correcting the deflection angle of thefirst galvano scanner 29 (step S22).

[0087] After making the machining, the positional precision of processedhole is measured with the CCD camera 36 by driving the XY stage 31. Whenit is out of the tolerance value, the program is ended to inform theoperator that the apparatus has an abnormality of the apparatus or thereis an error in usage of the method in the same manner as correcting thedeflection angle of the second galvano scanner 30 and a message with thecontents indicating that the program is abnormally ended is displayed onthe operation screen, not shown.

[0088] On the other hand, within the tolerance value, the correction forthe deflection angle of the first galvano scanner 29 is ended.

[0089] The automatic correction for the deflection angle of the galvanoscanner is performed, if any conditions are satisfied, for example, ifthe temperature of the galvano scanner main body or the peripheraltemperature is monitored to detect a temperature change, or when a fixedtime has passed. Thereby, the machining is always performed at stablepositional precision.

[0090] In this embodiment, means for conducting the laser light ofcircular polarization to the polarized beam splitter and separating thelaser light into beams is employed. However, though not shown in theembodiment, the linearly polarized light may be oscillated from thelaser oscillator and conducted at an angle of 45° with respect to thepolarization directions of reflection and transmission that areorthogonal to each other in the polarized beam splitter, whereby thesame effects are obtained.

EMBODIMENT 2

[0091] After separation into laser beams by the polarized beam splitter,the laser beams are circularly polarized again, or incident on thepolarized beam splitter at an angle of 45° with respect to thepolarization directions of reflection and transmission, whereby theseparation into laser beams is repeated, and the machining is made usingnot only two beams but also 2n laser beams.

[0092]FIG. 6 is a schematic constitutional view showing an example ofthe laser material processing apparatus in which third polarizing meansis added to make the machining using four laser beams.

[0093] In the constitution as shown in FIG. 6, a laser light of circularpolarization or linear polarization is oscillated and conducted from thelaser oscillator, not shown, and separated into laser beams by a thirdpolarized beam splitter 38. The optical path is constituted so that thepolarization direction of a laser beam 26 transmitted through the thirdpolarized beam splitter 38 and the polarization direction of a reflectedlaser beam 39 make an angle of 45° with respect to the polarizationdirections of reflection and transmission in the first polarized beamsplitters 25 and 25A. Thereby, the laser beam 26 is separated into thelaser beams 26 a and 26 b and the laser beam 39 is separated into thelaser beams 39 a and 39 b.

[0094] The optical path following the first polarized beam splitters 25and 25A has the same constitution as in the embodiment of the inventionas shown in FIG. 1, whereby the machining is made by applying four laserbeams on the workpiece.

[0095] The optical path lengths from the third polarized beam splitter38 for separation to the workpiece subject to the laser beams are madeequal, and the beam spot diameters of four separated laser beams aremade equal.

[0096] To adjust the beam splitter, by comparing the energy of laserbeam 26 (sum of laser beams 26 a and 26 b) when the first and secondshutters 34 a and 34 b are only opened, and the energy of laser beam 39(sum of laser beams 39 a and 39 b) when the third and fourth shutters 34c and 34 d are only opened, the third polarized beam splitter 38 isrotated to change the incident angle of laser light, so that the laserbeam 26 transmitted through the polarized beam splitter 38 and theenergy of reflected laser beam 39 may be equal, as shown in FIG. 7.

[0097] Thereafter, by comparing the energy of laser beam 26 a when thefirst shutter 34 a alone is opened and the energy of laser beam 26 bwhen the second shutter 34 b alone is opened, the first polarized beamsplitter 25 and the second polarized beam splitter 27 are rotated andadjusted so that the energy of laser beam 26 is equally divided into thelaser beams 26 a and 26 b (step S32).

[0098] Finally, by comparing the energy of laser beam 39 a when thethird shutter 34 c alone is opened, and the energy of laser beam 39 bwhen the fourth shutter 34 d along is opened, the first polarized beamsplitter 25A and the second polarized beam splitter 27A are rotated, andadjusted so that the energy of laser beam 39 is equally divided into thelaser beams 39 a and 39 b (step S33).

[0099] With the above adjustments, the energy balance of four laserbeams conducted to the workpiece 34 is enhanced.

[0100] For the automatic correction for the deflection angle of thegalvano scanner, the deflection angle of each galvano scanner iscorrected by detecting a deviation from the reference position with thelaser beams 26 a, 26 b, 39 a and 39 b in a state where any one of theshutters 34 is opened.

[0101] As described above, if the laser material processing apparatusaccording to this invention is employed, a difference in the quality orenergy between separated laser beams is equalized to improve theproductivity. Also, by making the optical path length of two separatedlaser beams equal, the beam spot diameters of two laser beams are madeequal. Also, a rotating mechanism is provided in the stationary portionof polarizing means, whereby there is the effect that the variation inthe energy of two laser beams separated is minimized less expensively.

[0102] Industrial Applicability

[0103] As described above, the laser material processing apparatusaccording to the invention is suitable for drilling the workpiece suchas the printed board.

1. A laser material processing apparatus for processing a workpiece insuch a way as to separate one laser light into two laser beams via firstpolarizing means, one laser beam being passed via the mirrors, the otherlaser beam being scanned biaxially by a first galvano scanner, andconduct two laser beams to second polarizing means for scanning via asecond galvano scanner, characterized in that an optical path isconstituted such that said laser beam transmitted through said firstpolarizing means is reflected by said second polarizing means, and saidlaser beam reflected by said first polarizing means is transmittedthrough said second polarizing means.
 2. The laser material processingapparatus according to claim 1, characterized in that two polarizingmeans are arranged so that the reflection surfaces may be opposed toeach other to form an optical path in which the separated laser beamshave the equal optical path length.
 3. The laser material processingapparatus according to claim 1 or 2, characterized in that a stationaryportion of polarizing means is provided with a rotating mechanism aroundan axis perpendicular to a surface containing the axes of two separatedlaser beams.
 4. The laser material processing apparatus according toclaim 3, characterized in that an energy balance of said laser beam isadjusted by changing a transmission factor of the laser beam transmittedthrough polarizing means by rotation of said rotating mechanism.
 5. Thelaser material processing apparatus according to claim 1, characterizedby further comprising laser beam selecting means for selecting any laserbeam from among the separated laser beams.
 6. The laser materialprocessing apparatus according to claim 5, characterized in that saidlaser beam selecting means controls a shutter provided on the opticalpath of each of the separated laser beams to be opened or closed to takeout the laser beam from any optical path.
 7. The laser materialprocessing apparatus according to claim 5 or 6, characterized by furthercomprising detection means for detecting an energy balance of laser beamon each optical path, in which the energy balance of each laser beamdetected by said detection means is adjusted to be almost equivalent. 8.The laser material processing apparatus according to claim 7,characterized in that said detection means consists of a power sensorprovided near an XY table on which the workpiece is laid.
 9. The lasermaterial processing apparatus according to claim 1, characterized inthat the separated laser beams have the equal optical path lengthbetween said first polarizing means and said second polarizing means.10. The laser material processing apparatus according to claim 1,characterized in that the deflection angle by which said first galvanoscanner scans is smaller than the deflection angle by which said secondgalvano scanner scans.
 11. The laser material processing apparatusaccording to claim 1, characterized in that each laser beam is reflectedby the same number of mirrors on each optical path formed between saidfirst polarizing means and said second polarizing means.
 12. The lasermaterial processing apparatus according to claim 1, characterized byfurther comprising third polarizing means provided between a laseroscillator and said first polarizing means, in which two laser beamsseparated by said third polarizing means are conducted to said firstpolarizing means and said second polarizing means and further separatedinto 2n components.